The normal at (ap2,2ap) on y2=4ax, meets the curve again at (aq2,2aq) then
Equation of normal at (at2,2at) isy+tx=2at+at3
∴y+px=2ap+ap3
It meets at (aq2,2aq)
⇒2aq+p(aq2)=2ap+ap3
2q+pq2=2p+p3
2(q−p)=p(p2−q2)
−2=p(p+q)
p2+pq+2=0